Formation testing tools with discrete openings, such as a multi-probe module, can withdraw formation fluid in a focused direction. With the multi-probe module, formation pressure can be monitored at the flowing probe and two or more observation probes, one positioned on the opposite side of the borehole on the same horizontal plane as the sink probe and others displaced vertically on the same azimuthal plane as the sink probe.
Permeability determination with the multi-probe module has received considerable attention. In particular, the detection and quantification of permeability anisotropy in the horizontal-vertical plane, kh/kv has been studied. The detection and quantification of permeability anisotropy within the horizontal plane has received no attention. Knowledge of such anisotropy can be critical for optimum design of reservoir drainage patterns, secondary and tertiary recovery projects, and stimulation treatments, to name but a few examples. Anisotropy within the horizontal plane usually creates three-dimensional anisotropy, with vertical permeability differing from both components (kx and ky) of horizontal permeability.